Insullation- How much is enough?

murman

Hi,
I will start site clearance and raft construction 5 weeks from now. Location 12 miles from Galway city. The house type is "story and half" with total floor area of 2900 ft sq. I have given the amount, type and supplier of insullation much thought but still haven't fully decided what to install.

Kingspan seem to be best in class but are very expensive. I've been told that there are equally good products out there and that you pay for the name with Kingspan.

One company called Polypearl offer a complete insullation package and are reluctant to price individual products. Their package includes:-
EcoBead (Platinum coloured) blown into 106mm cavity.
Aerodorm 100mm (accordian board) between rafters on sloped ceiling (Platinum).
Warmcel (cellulose fibre) blown onto flat ceiling to depth of 220mm.
EPS standard density aerofloor 60mm on grounf floor (white).

Apparently Aerobord are bringing out an improved product for ground insullation when underfloor heating is used. Price to be provided when available. They claim that they achieve a U value of 0.41 W/m"K. Quoted price incl vat is 4550+vat.

In addition, I reckon I will need to use Kingspan (or similar) TP10 insulated plaster board on sloping ceilings and possible TW56 on horizontal ceiling to safely combat heat loss.

Also, I'm inclined not to insulate the internal surface of all external walls given that I have full cavity insullation - good idea or not? I'd appreciate any feedback/suggestions on this topic.

thanks
murman

Goll Mac Morna

Insulation is vital to the comfort of your home.
However, before getting into the nitty gritty of U-values etc. you must first be confident that the workmanship that you do (or employ others to do) is going to be 1st class.

The best insulation in the world is only as good as how it has been installed.
I have heard and seen some horror stories, where insulation is missing or has sagged or is not against the internal wall in the cavity.

For my house I am trying to get down to the following U-values
Roof 0.8
Wall 0.16
Floor 0.8

Xtratherm and Quinn make similar product to KINGSPAN

I am using a mixture of KINGSPAN (walls and possibly roof) and AEROBORD (floors)for my own house.

yop

Out of interest what are lads putting under their unde florr heating, is it kingspan?

Goll Mac Morna

Kingspan or other phenolic or polyisocyanurate boards with foil seem to be the answer for underfloor.
In our own house we are trying to bring the U-values down so that we can have a small heating system with radiators for occasional use in v. cold weather.

Ogham

My advice is get some share in Kingspan - the profit you might make could cover the price of the insulation...

Seriously - we had Kingspan everywhere. I looked at others and especially for the dormer roof - the others would have had to be thicker to provide the same insulation.
I considered the blown insulation - but what swung me against it was the fact the fact that in the UK - the NHBC don't allow it on new houses in Scotland because of the wet/windy weather. The cavity gets closed by the insulation and damp can cross into the internal walls. The weather here in Ireland isn't too different to that in Scotland - so I didn't go down that road.

The roof slope was the worst to cope with - tp10 and the insulated plaster board too.

Good Luck


http://self-build-in-ireland.blogspot.com/

gregos

Goll Mac Morna wrote:

For my house I am trying to get down to the following U-values
Roof 0.8
Wall 0.16
Floor 0.8

Are those figures correct? Unless you've analysed it by the overall heat loss method, to meet current standards you need to be aiming at

Roof 0.20
Walls 0.27
Ground floors 0.25

Even then, your targets are too high.

Goll Mac Morna

Floor = 300mm of AEROBORD (already installed- concrete slab has been poured fully insulated at edges - dead build walls are also insulated)
Walls = 200mm full fill cavity (80mm polyisocyanurate + 120mm Bonded Bead)
Roof = 450mm of cellulose fibre or other suitable materials

Entire building has been assessed using heat loss software.

Thermal bridging will be controlled by careful detailing and also use of insulating blocks at window reveals, wall plate etc.etc.

The target might seem high but as I said we are "...trying to achieve these u-values..."

The current Building standards are a general standard for the entire industry and therefore are set at an attainable level.

No doubt they will change as time goes by, I am trying to stay a bit ahead of the minimum standards considering it is my own house where I plan to see out my days.

gregos

Sorry. I didn't mean too high as in good. I meant too high as in u-value too high.

Goll Mac Morna

Apologies Gregos, I have just spotted my error
0.8 for floor and walls should be 0.08. (probably will be 0.10 in practice)
I wrote the number (0.8) down without even thinking !!!

patrido

murman wrote:

Kingspan seem to be best in class but are very expensive. I've been told that there are equally good products out there and that you pay for the name with Kingspan.

Yep, there are cheaper and just as good alternatives. Xtratherm being one example. Rockwool are another. Because of the increased standards defined in the building regs, all the manufacturers have to be able to achieve the specified U-values. The better products just make it easier to attain those u-values. There is very little point in blindly going with Kingspan.

murman wrote:

Also, I'm inclined not to insulate the internal surface of all external walls given that I have full cavity insullation - good idea or not? I'd appreciate any feedback/suggestions on this topic.

If you don't insulate the internal surface, the inner leaf of the blockwork acts as a thermal mass (in the same way as the floor does in a ufh system). So it will take longer for the room to heat up, but it will retain the heat for longer. The relative merits are debatable in my view.

There are *always* benefits in opting for increased insulation - U-value is a measure of how much heat is lost per m2 and degrees of heat differential between outside and inside. so the lower you go, the less heat will be lost.

but beyond a certain point, it will become so expensive that it will never pay for itself, in terms of reduced heating costs. this may not be a factor, but usually is

the one additional advantage to insulating the internal surfaces is that, as Goll intimated, it is much more difficult to install cavity insulation well. unless you have done the work yourself, and can be certain that there are no gaps in the insulation, and that it is all pressed correctly against the inner leaf, then your u-value will be higher than the expected value.

murman

Thanks for the info guys. I'll certainly checkout xtratherm and Rockwool. Will need to consider frther full cavity insullation!!